The identification generally consists in recovering the identity of an individual based on one of his biometric data.
This is shown schematically in FIG. 1, where it is carried out by means of a system comprising a biometric database M storing biometric data b1, . . . , bN relating to respective individuals and previously obtained during a phase referred to as registration phase, and a biometric sensor C capable of acquiring such biometric data.
The biometric data can be of any type and relate to any characteristic of an individual, such as an iris, one or more fingerprints, minutiae, a face, the palm of a hand, a vein network of a finger or of a hand, a combination of the preceding characteristics, or others.
When an individual presents himself for an identification, a biometric data value b′ relating to this individual is obtained by means of the sensor C, then is compared, in turn, with each of the biometric data b1, . . . , bN until a correspondence with one of these biometric data, bi1, is established.
Using this biometric data bi1, an identity ii1 for the individual whose biometric data b′ has been acquired is found. This identity ii1 is for example stored in relation to the biometric data bi1.
An authorization is simply distinguished from the identification that has just been described by the fact that the biometric data bo obtained is not used to find the identity of the individual whose biometric data b′ has been acquired, but in order to grant any type of authorization to this individual, such as an authorization for access to a site, an authorization for the delivery of a product, of a document, or other. In a case of authorization, it is therefore possible to only require a response that b′ has been detected as coming from one of the individuals in the registration database but without trying to read or to return an identity (which may therefore need not be stored in this case).
Owing to the complex and unstable nature of biometric data, the succession of the aforementioned comparison operations leads to a significant quantity of calculations. Thus, the results of the identification or of the authorization are only available after a relatively long period of time. Moreover, the processing capacity required imposes the use of relatively bulky systems.
Some attempts have been made to limit the quantity of calculations, without degrading excessively the reliability of the identification or of the authorization.
The article “A fast search algorithm for a large fuzzy database” by Feng Hao, John Daugman, Piotr Zielinski, published in June 2008 in “IEEE Transactions on Information Forensics and Security” is one example of this.
It promotes the idea of applying transformations to iris binary codes, such as rotations, permutations and extractions, so as to only conserve digital values of limited size. Comparisons based on these digital values are therefore greatly simplified with respect to the aforementioned ones carried out directly on biometric data.
Another drawback of the techniques hitherto described resides in their low level of protection of the biometric data.
This is particularly true in the case where the biometric data b1, . . . , bN are directly employed.
Even if these biometric data are stored in the biometric database M in an encoded manner, an uncoded version of these biometric data is however manipulated by the system, notably for purposes of comparison with the acquired biometric data value b′.
Thus, a person of criminal intent having access to the system could get hold of an unprotected version of the biometric data. The preservation of the identity of the corresponding individuals is not therefore assured.
In the case where less memory-hungry digital values are utilized to replace the biometric data, in accordance with the teaching of the aforementioned article “A fast search algorithm for a large fuzzy database”, these digital values nevertheless provide information on the biometric data from which they originate. The identity of the corresponding individuals is therefore still not protected in this scenario.
One aim of the present invention is to improve the preservation of the identity of individuals whose biometric data has been acquired.